Ocular Anatomy
Key Anatomical Facts
The human eye is an organ which reacts to light for several purposes.
The eye is not properly a sphere, rather it is a fused two-piece unit. The smaller, less curved unit called the cornea, is linked to the larger unit called the sclera.
The cornea and sclera are connected by a ring called the limbus.The iris and its black center, the pupil, are seen instead of the cornea due to the cornea's transparency.
Dimensions differ among adults by only one or two millimeters. The vertical measure, generally less than the horizontal distance, is about 24 mm among adults, at birth about 16-17 mm. The eyeball grows rapidly, increasing to 22.5-23 mm (approx. 0.89 in) by the age of three years. From then to age 13, the eye attains its full size. The volume is 6.5 ml (0.4 cu. in.) and the weight is 7.5 g. (0.25 oz.)
The eye is made up of three coats, enclosing three transparent structures. The outermost layer is composed of the cornea and sclera. The middle layer consists of the choroid, ciliary body, and iris. The innermost is the retina, which gets its circulation from the vessels of the choroid as well as the retinal vessels, which can be seen in an opthalmoscope.
Within these coats are the aqueous humor, the vitreous body, and the flexible lens.
The aqueous humor is a clear fluid that is contained in two areas: the anterior chamber between the cornea and the iris and exposed area of the lens; and the posterior chamber, behind the iris and the rest. The lens is suspended to the ciliary body by the suspensory ligament (Zonule of Zinn), made up of fine transparent fibers. The vitreous body is a clear jelly that is much larger than the aqueous humor, and is bordered by the sclera, zonule, and lens.
